This invention relates to a multiple-needle tufting machine, and more particularly to a modular looper apparatus for a multiple-needle tufting machine.
The conventional hook bars for multiple-needle tufting machines are long bars extending transversely of the machine below the needles and the base fabric. A conventional cut-pile hook bar has deeply elongated slots formed through its bottom face and uniformly spaced for receiving the hooks which cooperate with the needles to form loops in the yarns carried by the needle. For a narrow gauge, multiple-needle tufting machine, the looper slots in the hook bar must be formed close together. The closeness of the spacing of the looper slots is limited by the thinness of the walls between the slots. Conventional loopers or hooks are held in their respective slots by individual set screws which are threaded into each slot and engage the opposed walls or lands of the slots. Thus, the thinness of the walls is further limited by the diameters of the set screws. Moreover, the threaded movement of the set screws tends to expand and warp the slot walls or lands.
One solution to spacing the looper slots closer together in a narrow gauge tufting machine is disclosed in the prior U.S. Pat. No. 3,635,177, issued to Larry P. Gable, et al for NARROW GAUGE HOOK BAR FOR TUFTING MACHINE on Jan. 18, 1972. The Gable patent discloses a hook bar having uniformly spaced, but staggered, looper slots formed alternately in the front and rear faces of the hook bar. Thus, the staggered front and rear slots receive two transverse rows of staggered hooks or loopers for cooperation with corresponding staggered needles. However, the hook bar disclosed in the Gable patent was primarily designed for a looper apparatus for forming narrow gauge loop pile.
Another method of spacing the hook slots closer together in a narrow gauge tufting machine is disclosed in U.S. Pat. No. 4,067,270 of Hoyt E. Short for "NARROW GAUGE CUT PILE TUFTING APPARATUS," in which the needles are staggered and the loopers are made quite thin and flexible for bending and veering around each of the corresponding staggered needles.
A further solution for spacing loopers and hook slots closer together in a narrow gauge machine is disclosed in U.S. Pat. No. 4,158,339 of Hoyt E. Short, issued June 19, 1979, for "NARROW GAUGE CUT PILE LOOPER APPARATUS." In this narrow gauge cut-pile tufting machine, the needles are staggered and the slots are formed in the front and rear faces of the hook bar. However, the slots are designed to extend along the top of the hook bar to receive and reinforce the elongated body portions of the specially constructed looper hooks.
Another type of hook bar or looper apparatus for mounting a plurality of looper hooks close together in order to provide a more narrow gauge for multiple-needle tufting machines, is disclosed in U.S. Pat. No. 4,217,837, of Max M. Beasley et al, issued Aug. 19, 1980, for "FINE GAUGE LOOPER APPARATUS FOR IN-LINE TUFTING MACHINE." In this looper apparatus, the hook slots are formed in an insert bar received in the front face of the hook bar, and the looper hooks are held in position by a plurality of clamp members threadedly secured to the hook block and against the front body portions of the looper hooks. The hook bars are made in the form of elongated modules which are mounted end-to-end and each of the clamp members is adapted to secure a limited number of hooks upon the hook bar module.
In recent times, a plurality of thin hooks have been mounted securely and precisely in a hook bar by casting the metal forming the hook bar around the pre-set hooks. However, although strength, rigidity, and precision are attained, nevertheless an entire cast module of hooks must be discarded if only a single hook becomes defective.
Several modular hook bars of solid material having various hook slot constructions for receiving the rearward projecting shank portions of looper hooks, are disclosed in the pending application of Max M. Beasley et al, Ser. No. 397,793, filed July 13, 1982, for "MODULAR LOOPER APPARATUS FOR NARROW GAUGE TUFTING MACHINE." This application is assigned to Tuftco Corporation, the same assignee of the instant application. Although the various hook bar structures disclosed in application Ser. No. 397,793 operate generally satisfactorily, nevertheless various difficulties have been encountered with such hook bar structures under actual operation conditions, such as warpage or bending of parts of the hook bar, disalignment of the looper hooks, and/or distortion of the looper hooks or the retaining parts of the hook bar.